Estimation Method for Attenuation Coefficient of Thermal Radiation in Thermal Insulators by Using Thermal Conductivity

Abstract

A new method of estimating the attenuation coefficients of thermal radiation in thermal insulators was proposed. This is a means of deriving the attenuation coefficient using thermal conductivity of thermal insulators. It has already been proposed that the effective thermal conductivity of thermal radiation in thermal insulators is proportional to T3/ρ, determined using the absolute temperature T and the bulk density ρ. On the other hand, the effective thermal conductivity of thermal radiation in porous media with a high porosity is generally proportional to T3/β, determined using the absorption coefficient β with respect to the thickness of the object. From the above relation, the estimation equation for the attenuation coefficient β/ρ was derived. By using this equation, the attenuation coefficient of porous media, as thermal insulators having an uneven bulk density, must be derived as the representative value of the specimen. Furthermore, the attenuation coefficients of three kinds of thermal insulators were also estimated.